1. Field of the Invention
The present invention relates to an image evaluation device and an image evaluation method for evaluating the quality of image.
2. Description of the Related Art
Various techniques have been developed to evaluate the quality of image (for instance, the presence/absence of blurring, camera-shake and the like occurred in an image captured by an imaging system such as a camera). Here, a technique for evaluating the quality of image based on an edge of the image has been disclosed (refer to Reference 1 to 3 (which are, JP-A 2006-019874 (KOKAI), JP-A 2006-172417 (KOKAI), and JP-A 2008-123346 (KOKAI), in order)). Reference 1 discloses a technique in which a histogram of an estimated value of edge width is computed for each direction, and if the histogram different among the directions, it is determined that the camera-shake has affected the image. Reference 2 discloses a technique in which an average of edge widths of an original image is estimated to evaluate the degree of blurring. Furthermore, Reference 2 discloses a technique in which direction of the camera-shake is estimated as the direction perpendicular to the direction in which an edge strength is maximum, an autocorrelation is calculated along the camera-shake direction, and a displacement of the minimum value of the autocorrelation is computed as a width of the camera-shake. Reference 3 discloses a technique in which an average of edge widths is computed for each direction, and if all the averages are equal to or less than a threshold value, it is determined that no blurring occurs. Furthermore, Reference 3 discloses a technique in which edge patterns are classified based on a pattern matching of coefficients of DCT, an edge width is estimated based on a representative value of edge widths previously computed for each classification, and a blur region is narrowed down by setting it as a part in which the estimated edge width is wide.